Congenital dermal sinus and filar lipoma located in close proximity at the dural cul-de-sac mimicking limited dorsal myeloschisis

Introduction: Limited dorsal myeloschisis (LDM) with nonsaccular (flat) skin lesions has features similar to those of congenital dermal sinus (CDS); both show a tethering tract extending from the skin lesion to the intraspinal space. CDS may be found within the fibroneural LDM stalk because of the shared origin of the LDM and CDS. Thus, it can be difficult to distinguish between LDM and CDS. We surgically treated a boy in whom CDS and filar lipoma were located in close proximity to each other at the dural cul-de-sac, mimicking flat LDM. Herein, we describe the comprehensive clinicopathological findings of this patient. Case presentation: The patient was noted at birth to have a small dimple in the lumbosacral region. Magnetic resonance images showed a slender tethering tract that started from the skin lesion, entered the dural sac through the dural cul-de-sac, and joined the low-lying conus at L2-3, which is characteristic of LDM. However, the operative and histopathological findings revealed that the epidural stalk was pure CDS, terminating at the dura, and that the intradural stalk was a filar lipoma. Both were present in close proximity at the dural cul-de-sac and were approximately 1 mm in diameter. Conclusion: The diagnosis of LDM and CDS should be established on the basis of a comprehensive analysis of clinical, neuroradiological, operative, and histopathological findings.